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CVE-2026-33219

NATS is vulnerable to pre-auth DoS through WebSockets client service

Published: Mar 25, 2026Updated: Mar 26, 2026 Sources: CVE List NVDCWE-770
NVD MITRE
5.3CVSSMEDIUM
EPSS Score
0.3%
Top 74.0%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Workaround Only

Description

NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. Prior to versions 2.11.15 and 2.12.6, a malicious client which can connect to the WebSockets port can cause unbounded memory use in the nats-server before authentication; this requires sending a corresponding amount of data. This is a milder variant of CVE-2026-27571. That earlier issue was a compression bomb, this vulnerability is not. Attacks against this new issue thus require significant client bandwidth. Versions 2.11.15 and 2.12.6 contain a fix. As a workaround, disable websockets if not required for project deployment.

CVSS Vector Breakdown

AV:NAC:LPR:NUI:NS:UC:NI:NA:L
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:NConfidentiality
None
I:NIntegrity
None
A:LAvailability
Low
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Weaknesses

CWE-770

Affected Products

nats-serverlinuxfoundation
Mixed
AI / ML / ml-framework
nats-servernats-io
On-prem
Databases / cache-message-queue
linuxfoundationoss-projectUSAI / MLaka yocto, pytorch, everest
nats-iooss-projectDatabases

Attack Graph

Products CVE Techniques Tactics

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Exploitability

Workaround Available

MITRE ATT&CK

1 technique
Impact
View detailed technique mapping

References

https://advisories.nats.io/CVE/secnote-2026-02.txt
advisories.nats.io
https://advisories.nats.io/CVE/secnote-2026-11.txt
advisories.nats.io
https://github.com/advisories/GHSA-qrvq-68c2-7grw
github.com
and 1 more references View all →

Timeline

Published
Mar 25, 2026
Last Updated
Mar 26, 2026

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